Xenoestrogens interfere with normal endocrine functioning and have been linked to reproductive and developmental abnormalities in wildlife species and causally associated with human disease. Estrogen receptors (ER) are primary targets of these compounds and elucidating their role in xenoestrogen-related dysfunction is the focus of this proposal. Our primary goal is to identify ER-specific suites of co-regulatory proteins in response to estradiol (E2) and the xenoestrogens DDE, nonylphenol, and PBDEs, and determine their effect on ER activation. We will test the hypothesis that varied transcriptional regulation of gene targets by E2 and xenoestrogens is dependent on assembly of specific ER protein complex formation. This premise will be tested in 4 specific aims which employ state-of-the-art proteomic and functional genomic technologies in appropriate cell lines (human breast and lung). Out first hypothesis is that ERs will recruit compound-specific suites of accessory proteins that correlate with downstream activity. To test this hypothesis, we will use a tandem-affinity purification (TAP) and/or promoter-affinity/immunoprecipitation strategy to isolate ER-interacting proteins following stimulation with E2 and xenoestrogens. From this, we will identify known and possibly novel proteins by a combination of MALDI-TOF/TOF and HPLC-QTOF mass spectrometry. We will also use reporter assays to determine the effect of each xenoestrogen on ER activity in these cell lines. In Specific Aim 2, we will use an alternate approach based on combination of surface plasmon resonance with mass spectrometry to identify ER coregulatory proteins and to quantitate the ligand-dependence of binding kinetics and affinity of the ER complexes with various response elements. Once co-accessory proteins are identified, we will test the hypothesis that (Specific Aim 3) a subset of these proteins are transcriptionally regulated in response to E2 and the contaminants and will be tested using quantitative RT- PCR. Specific Aim 4 will address whether ER-modulating proteins are differentially required for ligand-specific transcriptional activity by ERs. We will employ mRNA knockdown strategies (siRNA) to address the functional role of select co-regulatory proteins in ER activity by xenoestrogens. The long term goal of these studies is to elucidate mechanisms of gene regulation by environmental contaminants, and how these actions lead to diseases/dysfunction. The goal of our research is to increase our basic understanding of the molecular events crucial to development of adverse outcomes associated with xenoestrogen exposure. This work will lead to more appropriate risk assessment and future development of therapeutic strategies for endocrine-related diseases. PUBLIC HEALTH RELEVANCE: Individuals exposed to xenoestrogens may be at risk for impaired health. The rising incidence in certain cancers and other endocrine related diseases over the past few decades suggests exposure to environmental agents, such as xenoestrogens, may play a role in disease development and progression. Elucidation of the molecular mechanisms that may contribute to the production of hormonally relevant diseases will lead to improved patient diagnostics and therapeutics as well as establishing relationships between environmental exposures and adverse health conditions.